This invention relates generally to a semi-conductor thin film transistor, and more particularly, to a semi-conductor thin film transistor having a construction wherein leakage current between source and drain regions is reduced in the OFF state. Recently, the techniques for forming thin film transistors have been studied with increasing intensity. The development of these transistors can be applied to many fields such as thin type active matrix display panels using a lower cost insulating substrate, three dimensional integrated circuits wherein an active element such as a transistor is formed on a semi-conductor integrated circuit, an inexpensive image sensor of high performance, high density memory devices, and the like. However, the performance of these devices is deteriorated when using thin film transistors because of the leakage current between source and drain which occurs in the OFF state. Thin film transistors capable of rapid response and delivering high current suffer the most from leakage currents in the OFF state.
What is needed is a thin film transistor (TFT) which has excellent forward characteristics and has low leakage current in the OFF state.